Micro electromagnetically actuated latched switches

ABSTRACT

Micro-electromagnetically actuated latched miniature relay switches formed from laminate layers comprising a spring and magnet, electromagnetic coils, magnetic latching material, and transmission line with contacts. Preferably the miniature relay switches transmit up to about 50 W of DC or AC line power, and carry up to about 10 A of load current, with an overall volume of less than about 100 mm3. In addition to switching large power, the device preferably requires less than 3 V to actuate, and has a latching feature that retains the switch state after actuation without the need for external applied voltage or current.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/547,426, filed Nov. 19, 2014, which is a continuation of PCTApplication No. PCT/US2013/031980, filed Mar. 15, 2013, which claimspriority to U.S. Provisional Application No. 61/655,939, filed Jun. 5,2012, all of which applications are incorporated herein by reference.

FIELD

The embodiments described herein generally relate to relay switches andmore particularly, to electromagnetically actuated latched miniaturerelay switches and manufacturing techniques to facilitate manufacturingin large volumes or embedding in other electronic packages.

BACKGROUND INFORMATION

The demand in distributed power management and power-efficientalternatives is calling for a new wave of power control devices. Readyfor higher level integration, these new elements include micro sensorsand micro actuators to realize close-loop control of complex systems.For energy intensive applications, such as home and business appliances,lighting, solar energy and automotive, high voltage and/or high currentcircuit control devices play a critical role. Traditional macro-machinedrelays, micro electro-mechanical switches and semiconductor relays arenot best suited for the aforementioned applications. In particular,inter solar panel routing, smart power measuring, and industriallighting all require small, embeddable relays. These emergingapplications currently do not have suitable products for their needs.

Electro-mechanical relays and switches are in almost every majorelectrical system, especially those requiring moderate power (>10 w),such as automotive, industrial, residential, commercial power, andlighting. Macro-machined and assembled electromagnetic relays arelimited in miniaturization and integration. Although reliable industrialsolutions, current high current contact relays are difficult to fit in apackage 3000 mm³ or smaller. The design approach of traditional coilwinding and contact switch assembly intrinsically limits furtherminiaturization.

Although truly small in size, traditional micro electro-mechanicalswitches have faced major challenges in high power applications (>10 W).They are difficult to design using conventional silicon technology.Silicon MEMS devices (and their close variants, such as electro-formedmetal devices) generally result in closely spaced, fragile elements.Most switches use electrostatic actuation to move the switch arm intocontact with the mating electrical contact. This can only be done if theswitch arm is close to the actuating mechanism, and if the actuationforce is small. However, for high power applications, this isunacceptable. Power coupling across the small gap between conductors isappreciable at high power, self-charging occurs at high power resultingin self-actuating switches (the “hot switch” effect), and high powerapplications require that high current be passed through the conductingelements, which would destroy the thin membranes.

Solid-state relays (SSR) use a small control signal, usually opticallyisolated, to control a larger load current or voltage. SSRs have fastswitching times of the order of microseconds to milliseconds as well aslower latching current of tens of milliamps. However, the relativelyhigher insertion loss at “close” and the reverse leakage current at“open” both prevent SSRs from becoming the most energy efficient powermanagement device.

SUMMARY

The embodiments provided herein are directed to micro mechanical relayswitches and more particularly, to electromagnetically actuated latchedmicro relay switches. Preferably the miniature relay switches transmitup to about 50 W of DC or AC line power, and carry up to about 10 A ofload current, with an overall volume of less than about 100 mm³. Inaddition to switching large power, the device preferably requires lessthan 3 V to actuate, and has a latching feature that retains the switchstate after actuation without the need for external applied voltage orcurrent. The embodiments also relate to methods of manufacturing suchrelay devices directly within or on any of the following: lead frames,substrates, microelectronic packages, printed circuit boards, flexcircuits, and rigid-flex materials.

The illustrative embodiments use printed circuit boards and laminates tobuild MEMS relay devices, which are ideally suited to the needs of highpower applications, since they allow the creation of rugged, highlyconductive contacts, and allow relatively easy integration ofalternative technologies such as magnetic components forelectro-magnetic actuation. These small sized devices employ anelectromagnetic actuation component that directs electric currentthrough another contact in the “on” state, or provides an open circuitin the “off” state. The device requires low voltage to actuate, andrequires zero power to maintain either the “on” or “off” state(latching).

In one embodiment a movable component having a spring and magnet in alaminate layer is the main element of a single pole, single throw (SPST)electromagnetic micro relay. The movable component may be actuated by amechanism, such as electromagnetic actuation through the use of a coilin a laminate. If the tethered magnet is pulled close enough to thebottom region, a magnetic material in a laminate layer, such as a thinlayer of nickel, will hold the magnet down, thus latching it into the“on” state. The cantilever contains a conductive element coated on thesurface so it can act as an electric switch that connects two or moreelectrodes. The device is driven into a latched “on” state by using apulsed current through the coil. The device is also de latched byreversing the current pulse, thus creating reversed magnetic force topull the magnet away from the bottom. The magnet then latches on to thetop magnetic material to establish the “off” state of the switch.

The systems, methods, features and advantages of the invention will beor will become apparent to one with skill in the art upon examination ofthe following figures and detailed description. It is intended that allsuch additional methods, features and advantages be included within thisdescription, be within the scope of the invention, and be protected bythe accompanying claims. It is also intended that the invention is notlimited to require the details of the example embodiments.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included as part of the presentspecification, illustrate the presently preferred embodiment and,together with the general description given above and the detaileddescription of the preferred embodiment given below, serve to explainand teach the principles of the present invention.

FIG. 1 is a cross-sectional view of (a) an exploded assembly of laminatelayers and (b) an assembly of laminate layers of an embodiment of a SPSTelectromagnetic micro relay that shows all the basic components andcorresponding materials.

FIG. 2 is an isometric view of (a) an exploded assembly of laminatelayers and (b) an assembly of laminate layers of the embodiment show inFIG. 1.

FIG. 3 illustrates a laminate panel process for building micro relays atlarge scale by laminate panels.

FIG. 4 illustrates the use of conventional printed circuit boardmulti-layer process for building multiple layered electromagnetic coilswithin printed circuit boards.

FIG. 5 illustrates a device and method of closing and opening electriccircuits using a magnetic contact and electrodes on printed circuitboards.

FIG. 6 illustrates the use of low spring constant tethering foractuating magnet contact.

FIG. 7 illustrates dual-state latching micro relays.

FIG. 8 illustrates multiple sets of electromagnetic coils built withinthe same micro relay coils to produce intensive magnetic fields.

FIG. 9 illustrates electromagnetic coils with an iron core to produceNormally Open and Normally Close micro relays with significantlyincreased the magnetic force on the magnet contact.

FIG. 10 illustrates micro relays fabricated in laminates for use asautomobile relays.

FIG. 11 illustrates micro relays fabricated in laminates for use in homeand industrial lighting control.

It should be noted that the figures are not necessarily drawn to scaleand that elements of similar structures or functions are generallyrepresented by like reference numerals for illustrative purposesthroughout the figures. It also should be noted that the figures areonly intended to facilitate the description of the various embodimentsdescribed herein. The figures do not necessarily describe every aspectof the teachings disclosed herein and do not limit the scope of theclaims.

DESCRIPTION

The embodiments provided herein are directed to the micro mechanicalrelay switches and more particularly, to electromagnetically actuatedlatched miniature relay switches. Preferably the miniature relayswitches transmit up to about 50 W of DC or AC line power, and carry upto about 10 A of load current, with an overall volume of less than about100 mm³. In addition to switching large power, the device preferablyrequires less than 3 V to actuate, and has a latching feature thatretains the switch state after actuation without the need for externalapplied voltage or current. The embodiments also relate to methods ofmanufacturing such relay devices directly within or on any of thefollowing: lead frames, substrates, microelectronic packages, printedcircuit boards, flex circuits, and rigid-flex materials.

The embodiments refer to several techniques already disclosed in thefollowing applications, which are incorporated by reference: U.S.application Ser. No. 12/112,925: “Methods of manufacturing microdevicesin laminates, lead frames, packages, and printed circuit boards;” U.S.application Ser. No. 11/956,756: “Acoustic substrate;” U.S. applicationSer. No. 11/849,914: “High-Isolation Tunable MEMS Capacitive Switch;”U.S. application Ser. No. 10/751,131: “MEMS Fabrication on a LaminatedSubstrate.”

Since all relays will be eventually mounted on a substrate, such as aprinted circuit board, for system integration, it is preferable todesign and build them directly within a printed circuit board. Theillustrative embodiments use printed circuit boards and laminates tobuild MEMS relay devices, which are ideally suited to the needs of highpower applications, since they allow the creation of rugged, highlyconductive contacts, and allow relatively easy integration ofalternative technologies such as magnetic components forelectro-magnetic actuation. These small sized devices employ anelectromagnetic actuation component that directs electric currentthrough another contact in the “on” state, or provides an open circuitin the “off” state. The device requires low voltage to actuate, andrequires zero power to maintain either the “on” or “off” state(latching). The finished devices are automatically packaged within aprinted circuit board, whether singulated or panelized.

The embodiments of this disclosure introduce a micro electromechanicalrelay fabricated directly within printed circuit boards for moderate tohigh power applications. These devices simultaneously possess featuresthat are missing in other solutions, such as high power handling,embeddable small form factor, low insertion loss, high isolation, lowvoltage actuation and zero-power latching. In a detailed comparisonagainst existing relay devices (see Table 1 below), the embodimentsdescribed herein have an advantage on most features as standalonedevices. Collectively, embedded arrays and networks of these deviceswould show further benefits in larger scaled applications.

TABLE 1 Comparison Matrix Of The Present Disclosure Versus ExistingSolutions Macro-machined Solid State Present Relays MEMS Switches relaysembodiment Typical load 20 A 1 A 20 A 20 A current Typical switching 120V 10 V 120 V 120 V current Contact resistance 3 mOhm 1 Ohm N/A 0.2 OhmLeakage current 0 0 7 mA 0 Form factor 20 × 20 × 10 0.5 × 0.5 × 0.5 50 ×50 × 10 5 × 5 × 4 Switching speed 100 ms 25 us 0.1-1 ms 100 ms Control12 V/0.1 A 50 V 3 V/3 mA 3 V/1 A voltage/current Latching N N N N

Devices in accordance with the embodiments described herein arefundamentally different from existing products in both design andfabrication technology. For instance, micro devices in accordance withthe embodiments described herein employ an electromagnetic actuationmechanism that drives a permanent magnet with highly conductive alloy toreach different states of the relay. The magnet latches to paramagneticmaterials at each state and no power is needed to maintain the stateonce established. For example, in a single throw single pole relay, theconductive coating directs electric current through two adjacentcontacts in the “on” state, or provides an open circuit in the “off”state.

Turning to the figures, as shown in FIG. 1, a movable component 100having a spring 104 and magnet 106 in a laminate layer 105 is the mainelement of a single pole, single throw (SPST) electromagnetic microrelay 111. The movable component 104 may be actuated by a mechanism,such as electromagnetic actuation through the use of a coil 102 in alaminate 103. If the tethered magnet 106 is pulled close enough to thebottom region, a magnetic material 108 in a laminate layer 107, such asa thin layer of nickel, will hold the magnet down, thus latching it intothe “on” state. The cantilever contains a conductive element 110 coatedon the surface so it can act as an electric switch that connects two ormore electrodes 109. The device 111 is driven into a latched “on” stateby using a pulsed current through the coil. The device 111 is alsodelatched by reversing the current pulse, thus creating reversedmagnetic force to pull the magnet 106 away from the bottom. The magnet106 then latches on to the top magnetic material 101 to establish the“off” state of the switch.

As shown in FIG. 2, the laminates layers contain different mechanicaland electrical mechanisms, such as the movable spring load 205 with apermanent magnet 206 coupled to the spring load 205, the electromagneticcoil 203, the contact electrodes 207 coupled to a transmission line 209,and the magnetic material 201. All layers are laminated together to forma complete assembly with the mechanical elements enclosed in a package211. Conductive adhesives, such as solder paste and conductive epoxy,and non-conductive adhesives, such as pre-impregnated composite fibersand epoxy, are utilized at selective locations to satisfy differentbonding requirements.

In one preferred embodiment, the preferred elements of the device are 1)two multi-turn, six layer coils 203 produced in a 12-layer laminate toprovide an electromagnetic actuation force; 2) a polyimide spring 205which holds a 1 mm×0.25 mm gold-plated, neodymium permanent magnet 206with a polished surface; 3) a transmission/signal line 209 withnickel-gold contact pads 207; and 4) nickel plated regions 201 on thetop and under the contact pads to provide magnetic latching. Otherelements include structural layers to hold elements and provide openspace for the armature to move, and electrical vias.

During normal “OFF” operation, the permanent magnet remains latched tothe top of the device, held in place by magnetic attraction to the topnickel plate. During actuation to “ON” state, a low voltage, highcurrent pulse is passed through the coils producing an electromagneticforce ˜3 mN on the magnet and moving it towards the bottom plate, whichcontains a transmission/signal line that is designed with an open gap.When sufficiently close, the nickel plate on the bottom attracts themagnet causing it to. After this, the coil is completely de-energized.The polished gold coated magnet makes electrical contact with twopolished gold contact pads on the transmission/signal line and placesthe switch in the “ON” position. To actuate the device into the “OFF”state, a reverse current pulse is sent through the coils, causing themagnet to move back up and latch to the top plate.

Turning to FIG. 3, the laminate panel process enables large scaleproduction of hundreds or thousands of micro relays. Laminate panels(FIG. 3(a)) of movable spring loads 305, electromagnetic coils 303,contact electrodes 307, and magnetic material 301 (301-307) arelaminated to form a composite panel 309 (FIG. 3(b)) before beingsingulated by mechanical tools. Singulated micro relays 311 (FIG. 3(c))function as stand-alone devices.

As shown in FIG. 4, electromagnetic coils 400 are fabricated usingconventional printed circuit board multi-layer processes. Spiral coils404 on one layer direct the electric current to rotate clockwise orcounter clockwise. Each layer 405-415 alternates spiral directions inorder to maintain the same direction of electric current. Two contactpads 401, 403 are used as current terminals. Via holes 402 throughlayers are used to connect adjacent spirals 404. Up to 32 layers ofelectromagnetic coils can be fabricated by conventional printed circuitboards factories.

Referring to FIG. 5, line power up to 120 V peak voltage and 10 A peakcurrent 511 can be conducted through electrodes 503 through a magneticcontact 501 that are latched to “close” state. The contact surfacesbetween the magnet 501 and electrodes 503 are coated with lowresistance, low adhesion force material 502, such as gold nitride andplatinum alloy, which are durable for millions of hot switchingoperations. The conductive via 505, filled or unfilled, make electricalconnection from the packaged electrodes 503 to exposed surface mountablepads 507.

As shown in FIG. 6, highly flexible and durable thin film material, suchas polyimide and polyester, can be cut according to designed patterns601 by focused C02 laser cutter that are commercially available. Amagnet 603 is attached to the processed spring 605 using adhesives.Single sided 607 and double sided 609 attachments are useful for singleand double state switch designs, respectively.

Turning to FIG. 7, dual-state latching micro relays 701 consist of twosets of electromagnetic coils 707, 709 and two sets of contactelectrodes 705. The magnet and spring load mechanism 703 can be actuatedto latch on both top 713 and bottom 711, resulting in opening andclosing of opposing electrodes 705.

As shown on FIG. 8, multiple sets of electromagnetic coils 807 can bebuilt within the same micro relay 801 to gain stronger magnetic force toactuate relays with stronger latching force. In another device 803, thecoils 807 can locate on either side of the armature 804 for focusedmagnetic field flux. In a further device 805, magnetic field shapingmaterial 809, such as permalloy, is used to further confine the magneticfield flux to most effectively drive the floating magnet contact 806.

As shown in FIG. 9, iron cores 902 in the center of the electromagneticcoil 907 can significantly increase the magnetic force on the magnetcontact 906. The paramagnetic property of iron cores 902 causes themagnet contact 906 to latch on to the core 902 side, resulting in“Normally Open” 901 and “Normally Close” 903 micro relay configurations.

Turning to FIG. 10, two types of automotive relays can be manufacturedin accordance with the illustrative embodiments: standalone andembedded. In a typical sedan, over twenty standalone micro relayscontrol functions such as wipers 1005, flashers 1003, power steering1007, door locks 1013, dashboard electronics 1009, and defogger 1011.The embedded micro relays 1019 and switches 1015 and 1017 replace thetraditional automobile relay box 1001 with a relay board 1021.

In FIG. 11, an illustrated embodiment is a multi-channel lightingcontrol box 1105 with a number of micro relays described herein. Asingle 1101 or a panel 1103 of lights, such as incandescent, mercury andLED, can be controlled by a single relay unit. The control box 1105receives commands from the users through the internet 1109 enabledinterface such as a smart cellular phone 1111 and a personal computer1113.

While the invention is susceptible to various modifications, andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formsor methods disclosed, but to the contrary, the invention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the appended claims.

What is claimed:
 1. A latching micro-electro-mechanical relay switchcomprising: a first laminate layer comprising a moveable componentcomprising a spring and a magnet, a second laminate layer comprising acoil, the coil configured to actuate the moveable component, and a thirdlaminate layer comprising a magnetic material, the magnetic materialconfigured to hold the magnet of the moveable component, the magneticmaterial further configured to latch the magnet of the moveablecomponent into an “on” state, wherein the first, second and thirdlaminate layers are separate and distinct layers, and wherein the firstlaminate layer is positioned between the second laminate layer and thethird laminate layer.
 2. The switch of claim 1 wherein the first, secondand third laminate layers are laminated together.
 3. The switch of claim1, wherein the coil comprises a multi-turn, six layer coil.
 4. Theswitch of claim 1, wherein the coil comprises a six layer coil.
 5. Theswitch of claim 1, wherein the moveable component comprises a polyimidespring.
 6. The switch of claim 1, wherein the third laminate layercomprises a transmission/signal line.
 7. The switch of claim 6, whereinthe transmission/signal line comprises a plurality of contact pads. 8.The switch of claim 6, wherein the magnetic material is positioned belowthe plurality of contact pads to provide magnetic latching.
 9. Theswitch of claim 1, wherein contact surfaces between the magnet andcontact pads are coated with a conductive element coating.
 10. A switchaccording to claim 9, applied as a standalone micro relay controlfunction for one of windshield wipers, flashers, power steering, doorlocks, dashboard electronics, or defogger.
 11. The switch of claim 1,further comprising: a second electromagnetic coil for providingelectromagnetic energy to actuate the moveable component.
 12. The switchof claim 11, wherein the magnet and spring are actuated to latch themagnet on both the top and bottom of the switch.
 13. A standaloneautomotive micro relay control switch, comprising a switch according toclaim
 1. 14. An embedded automotive micro relay control switch,comprising a switch according to claim
 1. 15. A multi-channel lightingcontrol box, comprising at least one switch according to claim
 1. 16.The multi-channel lighting control box according to claim 15, configuredto control one or more lights.
 17. The multi-channel lighting controlbox according to claim 15, configured to control a panel of lights. 18.The multi-channel lighting control box according to claim 15, configuredto receive commands from a computing device via a network.
 19. Theswitch of claim 1, wherein the coil provides electromagnetic energy toactuate the moveable component.
 20. The switch of claim 1, wherein themagnet is driven to the latched “on” state when a pulsed current passesthrough the coil.
 21. The switch of claim 1, wherein the magnet isdriven to a delatched state when a pulsed current is reversed throughthe coil.
 22. A single pole, single throw (SPST) electromagnetic microrelay comprising a plurality of laminate layers, a movable componenthaving a spring and magnet in a first laminate layer of the plurality oflaminate layers, a magnetic material in a third laminate layer of theplurality of laminate layers, and an electromagnetic actuation mechanismin a second laminate layer of the plurality of laminate layers, whereinthe movable component is actuated by the mechanism to pull the movablecomponent close enough to the magnetic material to latch the movablecomponent in an “on” state, wherein the first, second and third laminatelayers are separate and distinct layers, and wherein the first laminatelayer is positioned between the second laminate layer and the thirdlaminate layer.
 23. The SPST of claim 22, wherein the electromagneticactuation mechanism includes an electromagnetic coil in the secondlaminate layer of the plurality of laminate layers.
 24. The SPST ofclaim 23, further comprising an iron core positioned within theelectromagnetic coil.